BEIJING, April 18 (Xinhuanet) -- Officials from U.S. Food and Drug Administration (FDA) announced Tuesday that the first vaccine for humans against bird flu will not be sold commercially.

    The vaccine made by French company Sanofi-Aventis is already being stockpiled for use if the strain mutated into a form that spread easily from person to person, sparking a pandemic.

    "The threat of influenza pandemic is one of the most important public health issues our nation faces today," Norman Baylor, director of the U.S. Food and Drug Administration's Office of Vaccines Research and Review, said at a teleconference.

    "This approval is an important step in enhancing the nation's readiness against a possible pandemic and enhances our ability to protect those who could be at increased risk of exposure," Baylor added.

    Baylor said the new vaccine is indicated for people aged 18 to 64 who are at "increased risk" of exposure to the H5N1 virus. Individuals would get two injections of 90 micrograms each, spaced about one month apart.

    Still, "we feel as part of pandemic preparedness it would be best to have a licensed vaccine. Our review suggests this vaccine is safe and effective," Baylor said.

    David Williams, president of Sanofi vaccine unit Sanofi Pasteur, said in a statement the approval was "a significant milestone in pandemic preparedness."

    Nearly 300 people have been infected by the H5N1 avian influenza virus worldwide since late 2003, according to the World Health Organization. The virus have killed 172 people so far.

    If it acquires the ability to pass person-to-person easily, it would spark a pandemic and scientists fear it could kill tens of millions of people.

    (Agencies)